PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties ... [more ▼]

PA nanocomposites are prepared from clays organophilized with a phosphonium and an ammonium salt, and sodium montmorillonite is used as reference. The analysis of mechanical and micromechanical properties of the composites reveal that several micromechanical deformation processes occur in the PA/MMT composites. The matrix cavitates at relatively small stress. Processes related to non-exfoliated clay structural units are initiated at larger stresses. Sound is emitted mainly by the fracture of particles, but debonding may also occur. The plastic deformation of the matrix dominates at larger stresses and deformations. The various local deformations are independent of each other and composite properties are not determined by silicate related processes but by the deformation of the matrix. [less ▲]

The use of organo-montmorillonite as nanofiller for the preparation of polymer nanocomposites still attracts a lot of attention both on experimental and industrial scale. In order to enlarge the range of ... [more ▼]

The use of organo-montmorillonite as nanofiller for the preparation of polymer nanocomposites still attracts a lot of attention both on experimental and industrial scale. In order to enlarge the range of organo-montmorillonites available for this application, supercritical carbon dioxide (scCO2) was used as a medium for the organomodification process. This environmentally friendly solvent showed a great potential to obtain ready-to-use organo-montmorillonite powders. Intercalation with high degrees of exchange was obtained when the surfactants (alkyl ammonium, phosphonium, and imidazolium salts) were in the liquid state at the reaction temperature. The addition of a small quantity of co-solvent enabled the intercalation of solid surfactants, such as those bearing hydroxyl or carboxyl groups. Basal spacings of montmorillonite modified in scCO2 corresponded to those measured for organo-montmorillonite prepared in the wet process. A detailed investigation of the reaction conditions was finally performed in order to up-scale the process. [less ▲]

Polyamide-6 nanocomposites were prepared from a new phosphonium organoclay obtained at pilot scale in supercritical carbon dioxide (scCO2) and a commercially available ammonium modified-silicate. The ... [more ▼]

Polyamide-6 nanocomposites were prepared from a new phosphonium organoclay obtained at pilot scale in supercritical carbon dioxide (scCO2) and a commercially available ammonium modified-silicate. The composites were homogenised by twin-screw extrusion, then specimens for testing were prepared by injection moulding. The clay content of the composites was varied from 0 to 7 vol% in 7 steps. The clays were characterised in detail; they differed in their surface coverage and gallery structure, while their particle size was similar and their surface energy differed only slightly. X-ray diffraction, electronic microscopy and rheology were used for the characterisation of composite structure. Different gallery structure of the clays led to dissimilar extent of exfoliation. The phosphonium organoclay exfoliated better in PA than the silicate treated with the ammonium salt in spite of its smaller surface coverage. The nanocomposites showed the usual complex structure: besides individual platelets and intercalated stacks, large particles were also present and the development of a silicate network could be shown at large clay contents. Quantitative determination of the extent of reinforcement revealed two determining factors: contact surface and strength of interaction. The first increases with exfoliation, but the latter decreases as an effect of organophilisation. The extent of exfoliation was also estimated quantitatively, and the calculation confirmed the results of qualitative evaluation showing larger extent of exfoliation for the scCO2-prepared phosphonium clay. [less ▲]

The organomodification of layered silicates via our patented supercritical CO2 ion-exchange process, enables the use of a large variety of surfactants, among which phosphonium and ammonium ions of the ... [more ▼]

The organomodification of layered silicates via our patented supercritical CO2 ion-exchange process, enables the use of a large variety of surfactants, among which phosphonium and ammonium ions of the very same structure. The as-obtained organoclays were melt blended with PA6 and the morphology as well as the fire properties of the nanocomposites were studied. With the same degree of nanodispersion, longer ignition times were observed with phosphonium-modified clays compared to ammonium-modified clays. [less ▲]

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater ... [more ▼]

In this study, the preparation of organoclays via a new process using supercritical carbon dioxide is described. This method turns out to be very efficient with various surfactants, in particular nonwater-soluble alkylphosphonium salts. The influence of the surfactant as well as of the clay nature on the thermal stability of the organoclay is evaluated by thermogravimetric analysis. Phosphonium-based montmorillonites are up to 90 °C more stable than ammonium-based montmorillonites. Moreover, the use of hectorite adds another 40 °C of thermal stability to the phosphonium-modified clays. These organomodified clays have been melt-blended with polyamide 6 and morphology as well as fire properties of the nanocomposites are discussed, in terms of influence of the stability of organoclays. For the first time, comparison of nanocomposites based on clay organomodified by ammonium and phosphonium salts of the very same structure is reported. [less ▲]

For the last two decades, intensive research has been focused on developing reinforced polymers with incorporation of nanometric fillers. Amongst the different types of nanofillers, those based on layered ... [more ▼]

For the last two decades, intensive research has been focused on developing reinforced polymers with incorporation of nanometric fillers. Amongst the different types of nanofillers, those based on layered silicates (commonly known as clays), have been most widely investigated. Dispersing clay sheets on a nanoscopic scale (so-called exfoliation) indeed allows materials with enhanced thermal, mechanical, rheological, flame retardancy and barrier properties to be produced. However, the nanocomposite performances are strongly dependent upon the extent of clay exfoliation. In order to enhance the compatibility between the pristine clay, hydrophilic, and the polymer, hydrophobic, and to achieve a good delamination of the nanolayers, an organo-modification of the clay is most usually necessary. This mini-review will provide an outline of patenting activity in the field of manufacturing organoclays through ionic exchange. The variety of organic modifiers and the diverse processing techniques will be detailed, aiming to extract the most relevant organoclays for successful nanocomposite formation at industrial scale. [less ▲]